Piston actuators are employed to perform mechanical tasks with precise timing and high reliability. A linear piston is slidably mounted within a cylindrical barrel. An energetic pyrotechnic charge, or propellant, is initiated within a sealed chamber to provide a pressure wave, which, in turn, imparts its force on the piston. The piston is propelled through the barrel, and the kinetic energy of the piston is employed by the system to perform mechanical work.
In contemporary designs, the piston is configured to travel in a linear motion through the cylindrical barrel. The barrel has a smooth internal wall of a diameter slightly larger than the diameter of the piston body. Such clearance between the piston and barrel is necessary, in order to allow for resistance-free linear motion of the piston. A consequence of the clearance is referred to in the art as gas xe2x80x9cblow-byxe2x80x9d, whereby a portion of the detonated charge gas escapes through the clearance region past the piston. Thus, the efficiency of the system is compromised. The blow-by gases tend to bounce off the internal front wall of the barrel and retreat back into the front face of the advancing piston, referred to as xe2x80x9cpiston retractionxe2x80x9d. This can further compromise the efficiency of the system.
To mitigate the effects of the xe2x80x9cblow-byxe2x80x9d phenomenon, O-rings have been introduced, in order to improve the seal on the piston, while still permitting piston travel. However, O-rings tend to erode as a result of heat and pressure, and tend to disintegrate under the high pressure of the explosive charge following detonation. Portions of the O-ring can therefore be released into the path of the piston, possibly hindering travel of the piston.
The present invention is directed to an energetic-based piston actuator system that overcomes the limitations of the contemporary embodiments. In particular, the present invention imparts a rotational motion in the piston in a manner that increases system efficiency and reliability.
In one aspect, the present invention is directed to an energetic-based piston actuator. The actuator includes a barrel having a cylindrical interior surface. A piston is provided in the barrel, the piston being slidable within the barrel and having an outer diameter less than an inner diameter of the interior surface of the barrel. A ring of malleable material is provided about the piston. The interior surface of the barrel includes rifling.
In a preferred embodiment, the rifling engages the ring when the piston is driven in a linear direction down the barrel, the rifling deforming the malleable material of the ring so as to induce a rotational motion in the ring, and a corresponding counter-rotation in the piston.
The piston preferably includes a body and a neck, the piston body having an outer diameter less than the inner diameter of the interior surface of the barrel, and the ring being mounted about the piston neck.
The rifling preferably comprises grooves and lands formed on the interior surface of the barrel. The rifling may be in the form of uniform twist rifling or gain rifling.
The piston may comprise fore and aft piston heads of an outer diameter less than the inner diameter of the barrel cylinder interior surface. In this case, the ring is positioned in a groove between the fore and aft piston heads.
The ring may be mounted rotatable relative to the piston, or alternatively may be fixed to the piston.
An energetic, for example in the form of a propellant or pyrotechnic, when detonated, drives the piston and ring in a longitudinal direction down the barrel. The energetic preferably comprises Bis-Nitro-Cobalt-3-Perchlorate.
In a preferred embodiment, the piston and barrel have a slip-fit relationship.
In another aspect, the present invention is directed to an energetic-based actuator. The actuator includes a barrel having rifling on an interior cylindrical surface. A piston in the barrel has a slip-fit relationship with the barrel, the piston having a longitudinal axis. A ring is mounted about the piston and is rotatable relative to the longitudinal axis of the piston such that when a pressure charge is induced on the piston, the piston is driven down the barrel in an axial direction along the longitudinal axis of the piston, the axial direction of the piston causing the ring to deform in the rifling, causing the ring to mesh with the rifling, and to rotate, as the piston travels in the axial direction.
In this manner, the rotating ring serves as a seal for preventing gas blow-by, and the rotating piston is more dynamically stable throughout its travel down the barrel, leading to improved system efficiency and accuracy.